Moisture containing cleansing articles have many uses in everyday life: In the personal hygiene area, moisture containing cleansing articles are used to help cleaning the skin of babies, children or adults after bowel movements. In cosmetics moisture containing cleansing articles can be used to clean facial skin or other body parts. For example moisture containing cleansing articles can be used to remove residues of make-up.
Moisture containing cleansing articles usually comprise a substrate and a lotion that helps removing residues from the skin and protects the skin from a too stringent abrasive or irritating effect. The lotion can be water based, oil-based and/or can be an emulsion of water and hydrophobic components.
When moisture containing cleansing articles are put in contact with human skin, the lotion plays a crucial role in the protection of the skin. Mechanical protection from abrasion, hydration of the skin, deposition of a protective layer, are among the most common desired effects.
In personal hygiene and cosmetic uses, skin condition, prior to the use of the moisture containing cleansing article, can be in a deteriorated state: Residues or feces, urine and perspiration, for example, have a pH that increases over time. They unbalance the natural, slightly acid pH of the skin and render it more susceptible to rash, redness and irritation.
Lotions for moisture containing cleansing articles can therefore be also designed to help restoring the natural pH balance of the skin, to a natural pH of about 5.5. To that effect lotion can be characterized by their pH (usually neutral or slightly acidic) and by their buffering capacity. The buffering capacity is an indication of how effective the lotion is in counteracting the increase over time of the pH of the residues of feces or urine (leading to an alkalinity of the skin environment) and to restore a natural skin pH.
It is of interest to evaluate the pH of moisture containing cleansing article lotions. In that regard, pH indicators are of many types: Sensors connected to an electronic system can provide a precise reading of pH. Classical titration by an acid is well known in the art. pH papers or pH stripes are simple indicators that provide a pH reading over a defined pH range. They usually comprise a dried indicator dye applied on a substrate (paper stripe or polymeric stick), that changes its color when immersed into an aqueous solution depending on the pH of the solution and thus provide a pH reading by comparison to a colored reference scale. pH paper sticks and pH measurement of body fluids are, for example, described in WO9838905A1 by James C. Caillouette. The association of feminine pads with a pH indicator is, for example, described in U.S. Pat. No. 5,823,953 by J. M. Richards and A. C. Roskin.
Moreover, it is also of interest to evaluate the buffering potential of various moisture containing cleansing article lotions. For instance some lotions can exhibit a neutral pH but have little effect on restoring the natural pH of the skin because they are ineffective in overcoming the pH increase over time of the residues of feces, urine or perspiration (leading to alkalinity of the skin environment). Some other lotions can exhibit both a neutral pH and a significant buffering potential and thus be much more efficient in restoring a natural skin pH balance. Net, measurement of pH is an indication of the effect of a lotion on skin but not sufficient to determine the efficiency of a lotion.
It is of interest to develop a simple test that would allow for the comparison of moisture containing cleansing article lotions as for their efficiency and ability to restore a natural pH of the skin. It is of interest to measure with this test, the pH of the lotion in a simple and visual way. It is of interest to measure the buffering potential of the moisture containing cleansing article lotions. It is finally of interest to develop a simple, fast, easy to use test to measure both the pH and the buffering potential of moisture containing cleansing article lotions. Such a test would be useful because it would allow users of wipe products to compare the effectiveness of the various products in helping to maintain a desirable skin pH.